/*

 * rdppm.c

 *

 * Copyright (C) 1991-1994, Thomas G. Lane.

 * This file is part of the Independent JPEG Group's software.

 * For conditions of distribution and use, see the accompanying README file.

 *

 * This file contains routines to read input images in PPM/PGM format.

 * The extended 2-byte-per-sample raw PPM/PGM formats are supported.

 * The PBMPLUS library is NOT required to compile this software

 * (but it is highly useful as a set of PPM image manipulation programs).

 *

 * These routines may need modification for non-Unix environments or

 * specialized applications.  As they stand, they assume input from

 * an ordinary stdio stream.  They further assume that reading begins

 * at the start of the file; start_input may need work if the

 * user interface has already read some data (e.g., to determine that

 * the file is indeed PPM format).

 */



#include "cdjpeg.h"		/* Common decls for cjpeg/djpeg applications */



#ifdef PPM_SUPPORTED





/* Portions of this code are based on the PBMPLUS library, which is:

**

** Copyright (C) 1988 by Jef Poskanzer.

**

** Permission to use, copy, modify, and distribute this software and its

** documentation for any purpose and without fee is hereby granted, provided

** that the above copyright notice appear in all copies and that both that

** copyright notice and this permission notice appear in supporting

** documentation.  This software is provided "as is" without express or

** implied warranty.

*/





/* Macros to deal with unsigned chars as efficiently as compiler allows */



#ifdef HAVE_UNSIGNED_CHAR

typedef unsigned char U_CHAR;

#define UCH(x)	((int) (x))

#else /* !HAVE_UNSIGNED_CHAR */

#ifdef CHAR_IS_UNSIGNED

typedef char U_CHAR;

#define UCH(x)	((int) (x))

#else

typedef char U_CHAR;

#define UCH(x)	((int) (x) & 0xFF)

#endif

#endif /* HAVE_UNSIGNED_CHAR */





#define	ReadOK(file,buffer,len)	(JFREAD(file,buffer,len) == ((size_t) (len)))





/*

 * On most systems, reading individual bytes with getc() is drastically less

 * efficient than buffering a row at a time with fread().  On PCs, we must

 * allocate the buffer in near data space, because we are assuming small-data

 * memory model, wherein fread() can't reach far memory.  If you need to

 * process very wide images on a PC, you might have to compile in large-memory

 * model, or else replace fread() with a getc() loop --- which will be much

 * slower.

 */





/* Private version of data source object */



typedef struct {

  struct cjpeg_source_struct pub; /* public fields */



  U_CHAR *iobuffer;		/* non-FAR pointer to I/O buffer */

  JSAMPROW pixrow;		/* FAR pointer to same */

  size_t buffer_width;		/* width of I/O buffer */

  JSAMPLE *rescale;		/* => maxval-remapping array, or NULL */

} ppm_source_struct;



typedef ppm_source_struct * ppm_source_ptr;





LOCAL int

pbm_getc (FILE * infile)

/* Read next char, skipping over any comments */

/* A comment/newline sequence is returned as a newline */

{

  register int ch;



  ch = getc(infile);

  if (ch == '#') {

    do {

      ch = getc(infile);

    } while (ch != '\n' && ch != EOF);

  }

  return ch;

}





LOCAL unsigned int

read_pbm_integer (j_compress_ptr cinfo, FILE * infile)

/* Read an unsigned decimal integer from the PPM file */

/* Swallows one trailing character after the integer */

/* Note that on a 16-bit-int machine, only values up to 64k can be read. */

/* This should not be a problem in practice. */

{

  register int ch;

  register unsigned int val;



  /* Skip any leading whitespace */

  do {

    ch = pbm_getc(infile);

    if (ch == EOF)

      ERREXIT(cinfo, JERR_INPUT_EOF);

  } while (ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r');



  if (ch < '0' || ch > '9')

    ERREXIT(cinfo, JERR_PPM_NONNUMERIC);



  val = ch - '0';

  while ((ch = pbm_getc(infile)) >= '0' && ch <= '9') {

    val *= 10;

    val += ch - '0';

  }

  return val;

}





/*

 * Read one row of pixels.

 *

 * We provide several different versions depending on input file format.

 * In all cases, input is scaled to the size of JSAMPLE.

 *

 * A really fast path is provided for reading byte/sample raw files with

 * maxval = MAXJSAMPLE, which is the normal case for 8-bit data.

 */





METHODDEF JDIMENSION

get_text_gray_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)

/* This version is for reading text-format PGM files with any maxval */

{

  ppm_source_ptr source = (ppm_source_ptr) sinfo;

  FILE * infile = source->pub.input_file;

  register JSAMPROW ptr;

  register JSAMPLE *rescale = source->rescale;

  JDIMENSION col;



  ptr = source->pub.buffer[0];

  for (col = cinfo->image_width; col > 0; col--) {

    *ptr++ = rescale[read_pbm_integer(cinfo, infile)];

  }

  return 1;

}





METHODDEF JDIMENSION

get_text_rgb_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)

/* This version is for reading text-format PPM files with any maxval */

{

  ppm_source_ptr source = (ppm_source_ptr) sinfo;

  FILE * infile = source->pub.input_file;

  register JSAMPROW ptr;

  register JSAMPLE *rescale = source->rescale;

  JDIMENSION col;



  ptr = source->pub.buffer[0];

  for (col = cinfo->image_width; col > 0; col--) {

    *ptr++ = rescale[read_pbm_integer(cinfo, infile)];

    *ptr++ = rescale[read_pbm_integer(cinfo, infile)];

    *ptr++ = rescale[read_pbm_integer(cinfo, infile)];

  }

  return 1;

}





METHODDEF JDIMENSION

get_scaled_gray_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)

/* This version is for reading raw-byte-format PGM files with any maxval */

{

  ppm_source_ptr source = (ppm_source_ptr) sinfo;

  register JSAMPROW ptr;

  register U_CHAR * bufferptr;

  register JSAMPLE *rescale = source->rescale;

  JDIMENSION col;



  if (! ReadOK(source->pub.input_file, source->iobuffer, source->buffer_width))

    ERREXIT(cinfo, JERR_INPUT_EOF);

  ptr = source->pub.buffer[0];

  bufferptr = source->iobuffer;

  for (col = cinfo->image_width; col > 0; col--) {

    *ptr++ = rescale[UCH(*bufferptr++)];

  }

  return 1;

}





METHODDEF JDIMENSION

get_scaled_rgb_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)

/* This version is for reading raw-byte-format PPM files with any maxval */

{

  ppm_source_ptr source = (ppm_source_ptr) sinfo;

  register JSAMPROW ptr;

  register U_CHAR * bufferptr;

  register JSAMPLE *rescale = source->rescale;

  JDIMENSION col;



  if (! ReadOK(source->pub.input_file, source->iobuffer, source->buffer_width))

    ERREXIT(cinfo, JERR_INPUT_EOF);

  ptr = source->pub.buffer[0];

  bufferptr = source->iobuffer;

  for (col = cinfo->image_width; col > 0; col--) {

    *ptr++ = rescale[UCH(*bufferptr++)];

    *ptr++ = rescale[UCH(*bufferptr++)];

    *ptr++ = rescale[UCH(*bufferptr++)];

  }

  return 1;

}





METHODDEF JDIMENSION

get_raw_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)

/* This version is for reading raw-byte-format files with maxval = MAXJSAMPLE.

 * In this case we just read right into the JSAMPLE buffer!

 * Note that same code works for PPM and PGM files.

 */

{

  ppm_source_ptr source = (ppm_source_ptr) sinfo;



  if (! ReadOK(source->pub.input_file, source->iobuffer, source->buffer_width))

    ERREXIT(cinfo, JERR_INPUT_EOF);

  return 1;

}





METHODDEF JDIMENSION

get_word_gray_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)

/* This version is for reading raw-word-format PGM files with any maxval */

{

  ppm_source_ptr source = (ppm_source_ptr) sinfo;

  register JSAMPROW ptr;

  register U_CHAR * bufferptr;

  register JSAMPLE *rescale = source->rescale;

  JDIMENSION col;



  if (! ReadOK(source->pub.input_file, source->iobuffer, source->buffer_width))

    ERREXIT(cinfo, JERR_INPUT_EOF);

  ptr = source->pub.buffer[0];

  bufferptr = source->iobuffer;

  for (col = cinfo->image_width; col > 0; col--) {

    register int temp;

    temp  = UCH(*bufferptr++);

    temp |= UCH(*bufferptr++) << 8;

    *ptr++ = rescale[temp];

  }

  return 1;

}





METHODDEF JDIMENSION

get_word_rgb_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)

/* This version is for reading raw-word-format PPM files with any maxval */

{

  ppm_source_ptr source = (ppm_source_ptr) sinfo;

  register JSAMPROW ptr;

  register U_CHAR * bufferptr;

  register JSAMPLE *rescale = source->rescale;

  JDIMENSION col;



  if (! ReadOK(source->pub.input_file, source->iobuffer, source->buffer_width))

    ERREXIT(cinfo, JERR_INPUT_EOF);

  ptr = source->pub.buffer[0];

  bufferptr = source->iobuffer;

  for (col = cinfo->image_width; col > 0; col--) {

    register int temp;

    temp  = UCH(*bufferptr++);

    temp |= UCH(*bufferptr++) << 8;

    *ptr++ = rescale[temp];

    temp  = UCH(*bufferptr++);

    temp |= UCH(*bufferptr++) << 8;

    *ptr++ = rescale[temp];

    temp  = UCH(*bufferptr++);

    temp |= UCH(*bufferptr++) << 8;

    *ptr++ = rescale[temp];

  }

  return 1;

}





/*

 * Read the file header; return image size and component count.

 */



METHODDEF void

start_input_ppm (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)

{

  ppm_source_ptr source = (ppm_source_ptr) sinfo;

  int c;

  unsigned int w, h, maxval;

  boolean need_iobuffer, use_raw_buffer, need_rescale;



  if (getc(source->pub.input_file) != 'P')

    ERREXIT(cinfo, JERR_PPM_NOT);



  c = getc(source->pub.input_file); /* save format discriminator for a sec */



  /* fetch the remaining header info */

  w = read_pbm_integer(cinfo, source->pub.input_file);

  h = read_pbm_integer(cinfo, source->pub.input_file);

  maxval = read_pbm_integer(cinfo, source->pub.input_file);



  if (w <= 0 || h <= 0 || maxval <= 0) /* error check */

    ERREXIT(cinfo, JERR_PPM_NOT);



  cinfo->data_precision = BITS_IN_JSAMPLE; /* we always rescale data to this */

  cinfo->image_width = (JDIMENSION) w;

  cinfo->image_height = (JDIMENSION) h;



  /* initialize flags to most common settings */

  need_iobuffer = TRUE;		/* do we need an I/O buffer? */

  use_raw_buffer = FALSE;	/* do we map input buffer onto I/O buffer? */

  need_rescale = TRUE;		/* do we need a rescale array? */



  switch (c) {

  case '2':			/* it's a text-format PGM file */

    cinfo->input_components = 1;

    cinfo->in_color_space = JCS_GRAYSCALE;

    TRACEMS2(cinfo, 1, JTRC_PGM_TEXT, w, h);

    source->pub.get_pixel_rows = get_text_gray_row;

    need_iobuffer = FALSE;

    break;



  case '3':			/* it's a text-format PPM file */

    cinfo->input_components = 3;

    cinfo->in_color_space = JCS_RGB;

    TRACEMS2(cinfo, 1, JTRC_PPM_TEXT, w, h);

    source->pub.get_pixel_rows = get_text_rgb_row;

    need_iobuffer = FALSE;

    break;



  case '5':			/* it's a raw-format PGM file */

    cinfo->input_components = 1;

    cinfo->in_color_space = JCS_GRAYSCALE;

    TRACEMS2(cinfo, 1, JTRC_PGM, w, h);

    if (maxval > 255) {

      source->pub.get_pixel_rows = get_word_gray_row;

    } else if (maxval == MAXJSAMPLE && SIZEOF(JSAMPLE) == SIZEOF(U_CHAR)) {

      source->pub.get_pixel_rows = get_raw_row;

      use_raw_buffer = TRUE;

      need_rescale = FALSE;

    } else {

      source->pub.get_pixel_rows = get_scaled_gray_row;

    }

    break;



  case '6':			/* it's a raw-format PPM file */

    cinfo->input_components = 3;

    cinfo->in_color_space = JCS_RGB;

    TRACEMS2(cinfo, 1, JTRC_PPM, w, h);

    if (maxval > 255) {

      source->pub.get_pixel_rows = get_word_rgb_row;

    } else if (maxval == MAXJSAMPLE && SIZEOF(JSAMPLE) == SIZEOF(U_CHAR)) {

      source->pub.get_pixel_rows = get_raw_row;

      use_raw_buffer = TRUE;

      need_rescale = FALSE;

    } else {

      source->pub.get_pixel_rows = get_scaled_rgb_row;

    }

    break;



  default:

    ERREXIT(cinfo, JERR_PPM_NOT);

    break;

  }



  /* Allocate space for I/O buffer: 1 or 3 bytes or words/pixel. */

  if (need_iobuffer) {

    source->buffer_width = (size_t) w * cinfo->input_components *

      ((maxval<=255) ? SIZEOF(U_CHAR) : (2*SIZEOF(U_CHAR)));

    source->iobuffer = (U_CHAR *)

      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

				  source->buffer_width);

  }



  /* Create compressor input buffer. */

  if (use_raw_buffer) {

    /* For unscaled raw-input case, we can just map it onto the I/O buffer. */

    /* Synthesize a JSAMPARRAY pointer structure */

    /* Cast here implies near->far pointer conversion on PCs */

    source->pixrow = (JSAMPROW) source->iobuffer;

    source->pub.buffer = & source->pixrow;

    source->pub.buffer_height = 1;

  } else {

    /* Need to translate anyway, so make a separate sample buffer. */

    source->pub.buffer = (*cinfo->mem->alloc_sarray)

      ((j_common_ptr) cinfo, JPOOL_IMAGE,

       (JDIMENSION) w * cinfo->input_components, (JDIMENSION) 1);

    source->pub.buffer_height = 1;

  }



  /* Compute the rescaling array if required. */

  if (need_rescale) {

    INT32 val, half_maxval;



    /* On 16-bit-int machines we have to be careful of maxval = 65535 */

    source->rescale = (JSAMPLE *)

      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

				  (size_t) (((long) maxval + 1L) * SIZEOF(JSAMPLE)));

    half_maxval = maxval / 2;

    for (val = 0; val <= (INT32) maxval; val++) {

      /* The multiplication here must be done in 32 bits to avoid overflow */

      source->rescale[val] = (JSAMPLE) ((val*MAXJSAMPLE + half_maxval)/maxval);

    }

  }

}





/*

 * Finish up at the end of the file.

 */



METHODDEF void

finish_input_ppm (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)

{

  /* no work */

}





/*

 * The module selection routine for PPM format input.

 */



GLOBAL cjpeg_source_ptr

jinit_read_ppm (j_compress_ptr cinfo)

{

  ppm_source_ptr source;



  /* Create module interface object */

  source = (ppm_source_ptr)

      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

				  SIZEOF(ppm_source_struct));

  /* Fill in method ptrs, except get_pixel_rows which start_input sets */

  source->pub.start_input = start_input_ppm;

  source->pub.finish_input = finish_input_ppm;



  return (cjpeg_source_ptr) source;

}



#endif /* PPM_SUPPORTED */

